1. Field of the Invention
Hydrocarbon feed streams containing mixtures of aromatic hydrocarbons and non-aromatic hydrocarbons are separated into aromatics lean streams and aromatics rich streams by contacting the hydrocarbon stream with an organic non-quaternary clathrate salt having a cation containing less than 16 carbon atoms. The clathrate salts selectively interact with the aromatic components of the hydrocarbon feed mixture. The organic non-quaternary clathrate salt possess non-quaternary cations such as phosphonium, ammonium, imidazolium, pyridinium and piperidinium and a monovalent or polyvalent anion. They can be represented by formula: ##STR1## wherein
R is a radical independently selected from the group consisting of hydrogen, linear or branched C.sub.1 -C.sub.12 alkyl, C.sub.5 -C.sub.12 cycloalkyl, C.sub.7 -C.sub.12 aralkyl and alkaryl and C.sub.6 -C.sub.10 aryl, including inert or unreactive substitutes therein and mixtures thereof, wherein the total number of carbon atoms in the total of the R radicals in the cation is less than 16;
n is 1-3;
m is 1-5;
Q is N or P;
A is a monovalent or polyvalent anion.
The separation is conducted either above the melting point of the clathrate salt but below the decomposition temperature of either the salt or the hydrocarbon feed or under conditions such that the salt goes into solution in the hydrocarbon feed. The clathrate salt is separated from the aromatic hydrocarbon with which it combines by e.g. washing with water.
2. Description of the Related Art
U.S. Pat. No. 4,359,596 describes the separation of aromatics from mixed aromatics/aliphatics hydrocarbon streams by liquid salt extraction. The liquid salts used are of the formula EQU [R.sub.4 Q][A]
wherein
Q is nitrogen, phosphorous or arsenic;
A is a monovalent or polyvalent anion;
R.sub.4 Q is a monovalent or polyvalent cation in sufficient numbers to render the salt electrically neutral;
R is a hydrocarbon radical independently selected from the group consisting of linear or branched C.sub.1- C.sub.20 alkyl, C.sub.5 -C.sub.10 cycloalkyl, C.sub.7 -C.sub.20 aralkyl and alkaryl, and C.sub.6 -C.sub.10 aryl, concluding inert or unreactive substitutes therein and mixtures thereof, wherein the total number of carbon atoms in the four R radicals totals at least 16 and wherein not more than one R radical is methyl. The separation is performed by contacting the hydrocarbon feed with the salt above the melting point but below the decomposition point of the liquid salt. The salt is seen to possess a cation which is quaternary and contains at least 16 carbon atoms.